The scenes of devastation were all too familiar after more than a dozen explosions ripped through Baghdad. Iraqis see signs of a return to sectarian violence.

Iraqi security forces and residents gather at the scene of a car bombing… (Karim Kadim, Associated…)

Reporting from Baghdad and Beirut —

Sirens wailed, smoke billowed and blood pooled on the pavement.

The scenes of devastation were all too familiar after more than a dozen explosions ripped through the Iraqi capital Thursday, killing at least 60 people and injuring nearly 200, just days after the last U.S. troops left the country.

The attacks, some of the worst in Iraq this year, came in the midst of a political standoff between the country's main Shiite Muslim and Sunni Arab factions. The dispute threatens to unravel a U.S.-backed power-sharing government, and is spreading anxiety over the prospect of a return to the sectarian bloodletting that devastated the country in recent years.

By nightfall, fear gripped the city and some residents were already talking about the need to arm themselves again.

"I am not a devoted religious person, nor connected to any party," said Hassan Hanoon, 45, as he swept away shards of glass and other debris from a suicide car bombing near his minimarket in the Shiite-dominated neighborhood of Karada. "It's just instinct. The other one is killing you.… You have to defend yourself. How? By killing the other one. You will be forced to carry a weapon."

U.S. officials had warned of the possibility of high-profile attacks as the military wrapped up its nearly nine-year campaign last week. But they said Iraq's security forces were up to the task of maintaining stability and that the U.S. would remain engaged with the country's political leadership.

Vice President Joe Biden, who has spoken with several Iraqi leaders this week, called the country's president, Jalal Talabani, on Thursday to support his efforts to bring Iraq's major ethnic and religious blocs together. Talabani is an ethnic Kurd.

"Time and again, the Iraqi people have shown their resilience in overcoming efforts to divide them," the White House said in a statement. "We continue to urge leaders to come together to face common challenges."

Republican leaders have sharply criticized President Obama for not trying harder to keep a U.S. military presence in Iraq. Sen. John McCain of Arizona said on CBS television Thursday that Iraq was "unraveling tragically."

"We are paying a very heavy price in Baghdad because of our failure to have a residual force there," he said.

Some analysts say the departure of U.S. troops has left a dangerous vacuum. Violence has ebbed since the height of the anti-U.S. insurgency and sectarian fighting in 2006 and 2007. But the government faces continuing problems from Sunni insurgents and private Shiite militias, some with close ties to Iran.

Resentment also continues to simmer among the Sunni Arab minority that dominated under Saddam Hussein and now feels marginalized. Some Sunnis are urging secession, or at least greater autonomy for Sunni-dominated regions.

"This crisis really is caused because there is pervasive distrust and an absence of institutions that can carry this kind of transition," said Joost Hiltermann, an Iraq expert at the International Crisis Group.

Prime Minister Nouri Maliki, a Shiite, has never trusted the Sunni politicians with whom he has been forced to share power, Hiltermann said.

This week, Maliki moved against two top Sunni political leaders, accusing Vice President Tariq Hashimi of running a death squad and calling for a vote of no confidence in his deputy, Saleh Mutlak, who had compared the prime minister to a dictator.

"In the past when he has tried this sort of thing we've strong-armed him into knocking it off," Stephen Biddle at the Council on Foreign Relations said of Maliki. "We're much less able to do that now. In part it's because he needs us less, in part it's because we're less able to intervene."

"The whole point is, by being there you make it substantially less likely that Maliki would try that kind of adventure," Biddle said.

A warrant for Hashimi's arrest was announced the day after the last U.S. troops left Iraq, heightening suspicion among many in the Sunni minority that Maliki was trying to sideline their representatives in the coalition government and consolidate his authority.

State television broadcast statements by three of Hashimi's bodyguards, who said they had been ordered to commit killings and stage bombings that targeted government officials at the height of the sectarian fighting. One of the men claimed that the vice president himself rewarded him with envelopes containing $3,000.

Hashimi angrily denied the claims at a news conference Tuesday and accused Maliki of using the country's security forces to persecute political rivals. He said he was ready to stand trial, but only in the semiautonomous Kurdish region in northern Iraq, where he has taken refuge.

On Wednesday, Maliki demanded that the Kurdish authorities hand over Hashimi to face terrorism charges in Baghdad and threatened to replace government members who won't work with him.